1. Field of the Invention
The present invention relates to a method and circuit for suppressing sequential "zeroes" data. More particularly, it relates to a method and circuit for suppressing sequential "zeroes" data by inserting "1" after required sequential "zeroes" data and using a frame forced out by the above insertion of "1" as useful data.
2. Description of the Related Art
Generally, when there are too many sequential "zeroes" in the data transmitted between a transmitter and a receiver, a repeater may fail, because the repeater cannot extract a clock signal.
For this reason, the too many sequential "zeroes" are conventionally suppressed by either scrambling or by detection of the sequential zeroes.
Scrambling, on the transmitter side, suppresses sequential "zeroes" data by adding random data from a random pattern generator to the sequential "zero" data and changing the "zeroes" data into different data, and subsequently, on the receiver side, the same random data are added to the different data received, and the above "zeroes" data is regenerated.
Detection of the sequential zeroes, on the transmitter side, allows suppression of the sequential "zeroes" data by changing the last bit of the required sequential "zeroes" data to "1", and subsequentially, on the receiver side, the received "1" is changed again to "zero". This method will be explained in detail hereinafter.
The present invention is related to an improvement of the method of detecting the above sequential zeroes.
This conventional sequential zeroes detecting method, in actuality, has been realized by converting the "zero" of an LSB (Least Significant Bit) of bandwidth compression coding data in a telephone communication network to "1", which does not have an important effect on the network when compared with the conversion of a "zero" of an MSB (Most Significant Bit). However, on the receiver side in the conventional sequential "zeroes" detecting method, it is impossible to judge whether or not a "1" received has been converted from a "zero" on the transmitter side. If the "1" received is judged to have been converted from a "zero" even if it has not been converted, the receiver treats the received "1" as a "zero".
Consequently, the receiver side produces data which is completely different from the data sent by the transmitter, and this tendency is amplified when the conventional method is used for predictive coding or differential coding of one of many bandwidth compression codings, since error differential codes are stacked.
As can be understood from the above, the conventional sequential zeroes detecting method easily causes a misconversion on the receiver side, and this is not suitable for bandwidth compression coding in a visual communication network.